Label-free and highly-sensitive detection of calcium ions using a silicon-on-sapphire light-addressable potentiometric sensor.

BACKGROUND: Ionic calcium (Ca2+) plays a crucial role in maintaining normal physiological and biochemical functions within the human body. Detecting the concentration of Ca2+ is of utmost significance for various purposes, including disease screening, cellular metabolism research, and evaluating drug effectiveness. However, current detection approaches such as fluorescence and colorimetry face limitations due to complex labeling techniques and the inability to track changes in Ca2+ concentration. In recent years, extensive research has been conducted in this field to explore label-free and efficient approaches. RESULTS: In this study, a novel light-addressed potentiometric sensor (LAPS) using silicon-on-sapphire technology, has been successfully developed for Ca2+ sensing. The Ca2+-sensitive LAPS achieved a wide-range detection of Ca2+, ranging from 10-2 M to 10-7 M, with an impressive detection limit of 100 nM. These advancements are attributed to the ultra-thin silicon layer, silicon dioxide layer, and solid-state silicon rubber sensitive membrane around 6 µm. Furthermore, the sensor demonstrated the ability to dynamically monitor fluctuations in Ca2+ concentration ranging from 10-9 M to 10-2 M within a solution. Its remarkable selectivity, specificity, and long-term stability have facilitated its successful application in the detection of Ca2+ in human serum and urine. SIGNIFICANCE AND NOVELTY: This work presents a Ca2+-sensitive sensor that combines a low detection limit and a wide detection range. The development represents the emergence of a label-free and rapid Ca2+ detection tool with immense prospects in home-based health monitoring, community disease screening, as well as cellular metabolism, and drug screening evaluations.

Engineering a universal and fully automatic analyzer for multichannel and on-site biochemical detection in body fluids.

OBJECTIVE: Rising concerns over wellness and aging have heightened the demand for convenient and efficient on-site health monitoring and disease screening. Current research, focused on specific biomarker detection, often neglects the complexities of sample matrix interference and the absence of a comprehensive, automated platform. To address these issues, we have developed a universal, fully automated analyzer for multifaceted, on-site biochemical analysis of body fluids. METHODS: This analyzer integrates automated sample pretreatment, automatic dilution, detection, and self-cleaning functionalities seamlessly. It is designed to detect a wide range of analytes, from small molecules to macromolecules, including ions and proteins, utilizing spectrophotometric sensing. After optimization, the analyzer achieves performance comparable to traditional Enzyme-Linked Immunosorbent Assay (ELISA), while significantly expanding its detection range through automated dilution. RESULTS: Demonstrations of small molecule detection include the simultaneous assessment of citric acid (CA) and oxalic acid (OA) in urine, achieving recovery rates between 96.65%-106.42% and 93.13%-112.50%, respectively. For protein detection, the analyzer successfully identified Cyfra21-1 in saliva with a recovery rate of 104.93%-111.31%. The pre-treatment process requires only 8.8 minutes, showing enhanced recovery rates for CA and OA at 97.8% and 97.6% respectively, which are superior and more rapid than manual methods. CONCLUSION: The exemplary pretreatment and detection performance of the analyzer underlines its effectiveness in multifaceted, on-site biomarker detection, establishing it as a promising and versatile tool for disease screening and health monitoring. SIGNIFICANCE: This analyzer offers a powerful technological solution for on-site fluid testing, advancing community health care by facilitating more reliable and rapid diagnostics.